In recent years, the requirements for data transfer capacity and reliable networks have increased. Standards have been developed in order to increase the speed and the capacity of optical access network systems.
Reliability of communication networks is an increasingly important parameter, accordingly protection schemes have been discussed in connection with passive optical networks (PONs) with the purpose of minimizing the geographical fault coverage due to faults in equipment and/or fiber infrastructure. Examples of the single and dual homing protection schemes are fiber duplex system (type-A scheme), OLT-only duplex system (type-B scheme), full duplex system (type-C scheme) and partial duplex system (type-D scheme).
A classical view of dual homing foresees two optical line termination devices (OLTs) in geographically different locations hosting users i.e. the optical network units (ONUs) in a type-B scheme protected fashion. That is, trunk fiber and OLT are duplex, one OLT is in operation and the other OLT is in standby, kicking in if the OLT fails or if the trunk breaks. ONUs and drop fibers are simplex, a typical deployment scenario of which an example is depicted in FIG. 1. In case a primary OLT 10 fails, a secondary OLT 11 in cold-standby takes over and puts the users 13, connected via a splitter 12, back in service. Classical dual homing use a core network 14 for traffic since the secondary OLT 11 is on cold standby. Moreover, the OLTs need to exchange user configuration data via the core network to establish service in case of a failure. Thus, it's a high cost solution.